If you want to change from 3 to 4 hours, you need to 逐少逐少慢慢加多D ml 給 BB drink and 不用定時 each 3 or 4 hours to 餵, you can 餵 BB when he feel 肚餓, usally when BB feel 肚餓, they will crying, you can try it
according to the nurse fr neonatal care unit,
if bb's body weight more than 3.1 kg
then u might feed him every 4 hours
of course, u should follow your b's preference la